Such a device is known from French Patent No. FR 3002574 B1. It comprises a sleeve intended to be fixed to the vehicle and an adjusting element, bearing a stop, which can slide in the sleeve in order to place the stop at a given height. The device is then locked by imposing a movement on the control element to place retaining lugs in locking grooves and to bring together teeth and grooves arranged respectively on the control elements and on the sleeve to block any movement of the control element and to fix the height of the stop.
The solution proposed in this document effectively allows the stop to be placed at a specific height. However, it does not allow this height to be easily adjusted, especially after the device has been placed in the locking position.